Objective To investigate the expression of serum ficolin⁃3 and pentraxin 3（PTX3）in patients with rheumatoid arthritis combined with lung interstitial disease（RA ⁃ ILD）. Methods From December 2020 to December 2021，65 rheumatoid arthritis（RA）patients in our hospital were enrolled as RA group；70 RA⁃ILD pa⁃ tients as RA⁃ILD group，and 80 healthy subjects as control group. Enzyme⁃linked immunosorbent assay（ELISA） was used to detect the expression level of serum ficolin⁃3 and PTX3；Pearson method was used to analyze the corre⁃ lation of ficolin⁃3 and PTX3 and their correlation with DAS28，ESR，RF，CRP and pulmonary function⁃related in⁃ dexes；ROC curve was drawn to analyze the diagnostic value of ficolin⁃3 and PTX3 in RA⁃ILD. Results The val⁃ ue of DAS28，ESR，RF and CRP in RA ⁃ ILD group was significantly higher than those in RA group and control group，and significant higher value was observed in RA group when compared with the control group（P < 0.05）. The value of FVC，VC and DLCO in RA⁃ILD group was significantly lower than that in RA group and the control group，and significant lower value was found in the RA group when compared with the control group（P < 0.05）. The expression level of serum ficolin⁃3 in RA⁃ILD group was significantly lower than that in RA group and control group，and the expression level in RA group was significantly lower than that in the control group. The expression level of serum PTX3 in RA⁃ILD group was the highest，followed by RA group and the control group（P < 0.05）. Correlation analysis showed that the expression level of ficolin⁃3 in serum of patients in RA⁃ILD group was negative⁃ly correlated with PTX3（P < 0.05）；ficolin⁃3 was negatively correlated with the value of DAS28，ESR，RF and CRP，and positively with the value of FVC，VC and DLCO（P < 0.05）；PTX3 was positively correlated with the value of DAS28，ESR，RF and CRP，and negatively with the value of FVC，VC and DLCO（P < 0.05）. The AUC of the combined diagnosis for RA⁃ILD with ficolin⁃3 and PTX3 was higher than that of ficolin⁃3 or PTX3 alone（Z = 6.787，P = 0.009；Z = 15.492，P < 0.001）. Conclusion The expression level of ficolin ⁃3 in serum of patients with RA⁃ILD is significantly decreased，and the expression level of PTX3 is significantly increased. The combina⁃ tion of the two has certain diagnostic value for RA⁃ILD.